v POLYMORPHA LEPTINIDAE SILPHIDAE 221 



in curious places, including the nests of mice and bumble-bees. 

 In America, it has been found 011 the mice themselves by Dr. 

 Ryder, and by Riley in the nests of a common field-mouse, 

 together with its larva, which, however, has not been described. 

 The allied genus Leptinillus is said by Riley to live on the 

 beaver, in company with Platypsyllus. 1 It has been suggested 

 that the natural home of the Leptinus is the bee's nest, and 

 that perhaps the beetle merely makes use of the mouse as a 

 means of getting from one nest of a bumble-bee to another. 



Fam. 15. Silphidae. The mentum is usually a transverse 

 plate, having in front a membranous hypoglottis, which bears the 

 exposed labial palpi, and immediately behind them the so-called 

 bilobed ligula. The anterior coxae are conical and contiguous : 

 prothoracic epimera and episterna not distinct. Visible abdomi- 

 nal segments usually Jive, but sometimes only four, or as many as 

 seven. Tarsi frequently Jive-jointed, but often with one joint less. 

 Elytra usually covering the body and free at the tips, but occasion- 

 ally shorter than the body, and even truncate behind so as to expose 

 from one to four of the dorsal plates ; but there are at least three 

 dorsal plates in a membranous condition at the base of the abdomen. 

 These beetles are extremely diverse in size and form, some being 

 very minute, others upwards of an inch long, and there is also 

 considerable range of structure. In this family are included 

 the bury ing-beetles (Necrophorus), so well known from their habit 

 of making excavations under the corpses of small Vertebrates, 

 so as to bury them. Besides these and Silpha, the roving 

 carrion - beetles, the family includes many other very different 

 forms, amongst them being the larger part of the cave-beetles 

 of Europe and North America. These belong mostly to the 

 genera Bathyscia in Europe, and Adelops in North America ; but 

 of late years quite a crowd of these eyeless cave-beetles of the 

 group Leptoderini have been discovered, so that the European 

 catalogue now includes about 20 genera and 150 species. The 

 species of the genus Catopomorphus are found in the nests of 

 ants of the genus Aphaenogaster in the Mediterranean region. 

 Scarcely anything is known as to the lives of either the cave- 

 Silphidae or the myrmecophilous forms. 



The larvae of several of the larger forms of Silphidae are well 

 known, but very little has been ascertained as to the smaller forms. 



1 Insect Life, i. 1889, pp. 200 aiid 306. 



